Impact of ice ages on circumpolar molecular diversity: insights from an ecological key species

International audienceWe address the impact of the ice age cycles on intraspecific cpDNA diversity, for the first time on the full circumboreal-circumarctic scale. The bird-dispersed bog bilberry (or arctic blueberry, Vaccinium uliginosum) is a key component of northern ecosystems and is here used to assess diversity in previously glaciated vs. unglaciated areas and the importance of Beringia as a refugium and source for interglacial expansion. Eighteen chloroplast DNA haplotypes were observed in and among 122 populations, grouping into three main lineages which probably diverged before, and thus were affected more or less independently by, all major glaciations. The boreal 'Amphi-Atlantic lineage' included one haplotype occurring throughout northern Europe and one occurring in eastern North America, suggesting expansion from at least two bottlenecked, glacial refugium populations. The boreal 'Beringian lineage' included seven haplotypes restricted to Beringia and the Pacific coast of USA. The 'Arctic-Alpine lineage' included nine haplotypes, one of them fully circumpolar. This lineage was unexpectedly diverse, also in previously glaciated areas, suggesting that it thrived on the vast tundras during the ice ages and recolonized deglaciated terrain over long distances. Its largest area of persistence during glaciations was probably situated in the north, stretching from Beringia and far into Eurasia, and it probably also survived the last glaciation in southern mountain ranges. Although Beringia apparently was important for the initial divergence and expansion of V. uliginosum as well as for continuous survival of both the Beringian and Arctic-Alpine lineages during all ice ages, this region played a minor role as a source for later interglacial expansions

Twenty of the most thermophilous vascular plant species in Svalbard and their conservation state

An aim for conservation in Norway is preserving the Svalbard archipelago as one of the least disturbed areas in the Arctic. Information on local distribution, population sizes and ecology is summarized for 20 thermophilous vascular plant species. The need for conservation of northern, marginal populations in Svalbard is reviewed, using World Conservation Union categories and criteria at a regional scale. Thirteen species reach their northernmost distribution in Svalbard, the remaining seven in the western Arctic. Nine species have 1-8 populations in Svalbard and are assigned to Red List categories endangered or critically endangered: Campanula rotundifolia, Euphrasia frigida, Juncus castaneus, Kobresia simpliciuscula, Rubus chamaemorus, Alchemilla glomerulans, Ranunculus wilanderi, Salix lanata and Vaccinium uliginosum, the last four species needing immediate protective measures. Five species are classified as vulnerable: Betula nana, Carex marina ssp. pseudolagopina, Luzula wahlenbergii, Ranunculus arcticus and Ranunculus pallasii. Six species are considered at lower risk: Calamagrostis stricta, Empetrum nigrum ssp. hermaphroditum, Hippuris vulgaris (only occurring on Bjørnøya), Juncus triglumis, Ranunculus lapponicus and Rhodiola rosea. The warmer Inner Arctic Fjord Zone of Spitsbergen supports most of the 20 target species and is of particular importance for conservation. Endangered or vulnerable species were found in a variety of edaphic conditions; thus, several kinds of habitats need protection

The Antarctic and South American species of Deschampsia: phylogenetic relationships and cytogenetic differentiation

Deschampsia P. Beauv. is a cosmopolitan grass genus, which grows in cold and temperate regions, including about 15 species growing in South America and Antarctica. The species delimitation is difficult due to the high phenotypic plasticity and the likely occurrence of hybridization which generates species complexes with high morphological affinity. This work aims to describe the cytogenetic traits of the South American species of Deschampsia, highlighting similarities and differences in a phylogenetic context. We report the chromosome number of seven species of Deschampsia and Deyeuxia eminens for the first time, verifying that basic chromosome number x = 13 is shared by all the species. We found that the phylogenetic relationships are in agreement with the morphological affinities described in the species revisions, and the species of Deschampsia and Deyeuxia Sect. Stylagrostis form a well-supported clade. Despite the variation from x = 13 reported for populations of Deschampsia in the northern hemisphere, all the South American and Antarctic taxa studied here have a conserved basic chromosome number. Polyploids were found in several species, which suggests that genomic duplication is a recurrent process in the evolutionary history of Deschampsia. In contrast with the conserved chromosome morphology, the rDNA pattern showed high intra- and inter-specific variability and it is related to the phylogeny. Particularly, the complex of D. cespitosa is polymorphic for the distribution pattern of rDNA, as was also seen for molecular and morphological traits. Our results suggest that the common ancestor between Deschampsia and Deyeuxia sec. Stylagrostis could have had chromosomal characteristics currently shared by both. The incorporation of new chromosomal, molecular, and morphological data in Deyeuxia species will allow clarification of the close phylogenetic relationship with Deschampsia, in which reticulation and hybridization events cannot be excluded.Fil: González, María Laura. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; ArgentinaFil: Chiapella, Jorge Oscar. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Patagonia Norte. Instituto de Investigaciones En Biodiversidad y Medioambiente. Subsede San Martín de Los Andes-inibioma | Universidad Nacional del Comahue. Centro Regional Universitario Bariloche. Instituto de Investigaciones En Biodiversidad y Medioambiente. Subsede San Martín de Los Andes-inibioma.; ArgentinaFil: Urdampilleta, Juan Domingo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; Argentin